Antifreeze compositions are additives commonly used to lower the freezing point or increase the boiling point of water. Such additives primarily consist of one or more alcohol and/or glycol-based components. The most commonly used antifreeze component consisting of ethylene glycol. When added to an internal combustion engine cooling system at 50% volume concentration it affords the engine coolant contained therein freeze protection down to about -34.degree. F. and antiboil protection up to about 235.degree. F., depending on the pressure.
It is known that from the time the antifreeze is added to an aqueous-based engine cooling system the glycol and/or alcohol-based components of the antifreeze start to break down chemically into various organic acids. The organic acids produced are usually glycolic, formic and to a lesser extent oxalic and glyoxalic acids. The break down is confirmed by the pH of the engine coolant composition decreasing from a pH of about 10.0 downward toward a pH of 7.0.
Coolants circulating through an engine cooling system at a pH below 8.3 show a very corrosive effect on all metals comprising or located within the system. It is believed that at a pH of about 9 the corrosion effect starts and proceeds at a relatively slow rate until a pH of about 8.7 is reached. When the pH of the coolant is below 8.3 the corrosion proceeds at a very rapid rate. The less noble metals steel, iron and cast iron in a coolant system are the first to go into solution via the corrosion process. Low pH causes aluminum pitting which readily weakens the wall thickness of its respective components. Copper likewise corrodes and goes into solution. Zinc, used to strengthen silver solder in radiators, leaches out and weakens the solder so that leaks develop. The remaining impurities commonly found are suspended particulate matter primarily corrosion products (metal oxides), dirt, silt and hard water salt deposits.
Circulating coolant compositions generally include several known corrosion inhibitors. The inhibitors are added either directly to the coolant or included in the antifreeze solution added thereto which is sold as "inhibited antifreeze". However, typical corrosion inhibitors such as phosphates, silicates, borates, nitrites, nitrates, azols and molybdates are consumed over a period of time which further contributes to the corrosion effect on the engine cooling system.
It is generally accepted practice to remove and replace the coolant composition after a period of time. The initial coolant accumulates dissolved impurities and suspended particulate matter and looses effective corrosion inhibition and freeze protection capabilities with time. Although separate cooling system additives may be employed to neutralize degradation products accumulating in the system, these additives are primarily alkaline and include corrosion inhibitors, dispersants, polymers and sequestrants. Such compounds do not restore the depleted antifreeze components, i.e., glycol and/or alcohol, remove the impurities, nor increase the freeze protection or raise the boiling point of the degraded or used coolant, or inhibit further degradation of the glycol derivative.
Furthermore, a shortage of antifreeze, i.e., ethylene glycol is becoming predominately apparent throughout the United States. This will result in large increases in the price of antifreeze to the consumer. Also, in some states antifreeze is considered a hazardous waste and the Federal EPA and various State environmental agencies are imposing large fines on any facility that discharges antifreeze to the environment. Therefore, a need exists for a process of restoring or treating degraded or used engine coolants containing one or more antifreeze components to yield a recycled product which may be reintroduced into an internal combustion engine cooling system.